White Sharks are ‘Disappearing’ Here’s Why

3 September, 2019

by SEAN KELLY

Moving on from the Amazon, you’re news feed and google alerts might have been subject to the onslaught of headlines titled ‘Great Whites Are Disappearing and Nobody Knows Why’ or some derivative of that. The topic has even made its way out to backline, as if anyone needed to be reminded of big fish whilst surfing. After working in the shark conservation industry I thought I’d dig a little deeper and put the rather misleading headlines to bed. After all if there’s one species on the planet that commands respect, it’s the G-White! So here’s the story.

Although being mostly true, as far as highlighting the absence of great white sharks in False Bay, the headlines blasted on socials have created an air of confusion for shark cage diving tourism in the cape. The information supporting the claims are a result of the following:

1.) In 2018 Shark Spotters recorded 50 sightings, this year, not a single great white has been spotted both along the inshore area of False Bay or at Seal Island.

2.) The Shark Spotters’ applied research programme has failed to detect any of the tagged great whites on their tracking receivers since 2017.

3.) The arrival of the famed orcas, Port and Starboard has had a significant effect on the distribution of white sharks in the area.

4.) The lack of any feeding or bite marks on the whale carcasses the City has removed from False Bay this year.

5.) Shark cage diving ecotourism operators, who would normally witness multiple individual sharks visiting their vessels and up to 30 seal predations daily, have not had a single sighting at Seal Island this year.

All valid points and supported by empirical evidence. Thats not the misleading part, it’s the ‘nobody knows why’ that’s throwing the internet. So let me unpack it for you.

As a protected and critically endangered species, great white numbers are vital to have a handle on from a data point of view as only around 532 individuals remain. Putting a number on anything changes perspective especially so in an area that is considered to have the densest population of great white sharks in the world. This is where the value of shark cage diving proves invaluable according to Wilfred Chivell, the owner of Marine Dynamics:

“Shark cage diving is the only crucial monitoring platform of white sharks in South Africa. Whilst this species is protected in our waters it is facing many threats, that includes natural predators such as a pair of orcas specialising in hunting sharks for their livers, and human threats of industrial fisheries, pollution and environmental pressures, as well as illegal fishing.”

“Whilst we had a couple of tough years as the white sharks shifted their territory in 2017 and 2018, we have been enjoying incredible white shark sightings in Gansbaai over the past few months. Marine Dynamics has a daily blog that highlights sightings. The confusion created by a misleading headline can have negative ramifications on tourism”

At the moment, marine conservationists and shark scientists believe the reasoning behind the white sharks disappearing act, as stated above, to be a combination of factors.

Alison Towner, a resident shark biologist in Gansbaai had the following to say:

“Our team was involved in the research and monitoring of white shark behaviour pre and post orca presence in the Gansbaai area, as well as the necropsies on the white sharks that washed up over two years ago – we have a study being published on these results. When dealing with transient marine predators many facts must be considered. White sharks are highly migratory animals spending an average of a few weeks in any one area. We know that they respond to a natural predator and our observations support similar distribution shifts seen in California and Australia. However, many other factors influence their distribution, and we believe it is a combination of pressures leading to the shifts we are seeing in South Africa.”

Shark Spotters CEO, Sarah Waries, believes the sharks have moved further up the east coast due to, you guessed it, orcas and environmental conditions.

“There seems to be a shift eastwards, so that is why there has been an increase in activity in the Mossel Bay and Algoa Bay area. So it could be for some reasons whether it’s orcas or environmental conditions the sharks have appeared to have moved further up the east coast.”

Movement patterns of white sharks are complex and while we have learnt a lot over the last ~20 years, we still have a lot to learn. White sharks can live for more than 70 years of age, and their movement patterns change between the different stages of their lives e.g. juvenile sharks spend their time along the coast, while adults spend a lot of time away from the coast. These movements are also different between males and females and even between individuals. Furthermore, white shark movements are influenced by the environment e.g. water temperatures and food availability. They are generalist predators (which means they feed on a wide range of species) and are tolerant of a wide range of temperatures (although they seem to prefer 14 – 24 °C). They have a large home range encompassing the South West Indian Ocean and are capable of large migrations, and when conditions are not good in one place they can move to a better place.

The behaviour of animals is complex and the ocean is a dynamic ecosystem with natural cycles influenced by human activities. The disappearance of white sharks in False Bay is a mystery, and with all good mysteries there are many theories.

So in conclusion, yes white sharks seem to have taken a sabbatical in False Bay, shifting their territory eastward. Are they entirely absent, well unless you’re Aquaman and can speak to the fish, it’s difficult to say so with 100% certainty. Do the most qualified people in the business have an idea why such a shift is occurring, yes they do. So now that you’re armed with the facts go forth and share.

Shark Spotters will continue to operate over the 2019/2020 summer period at the following beaches:

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2 Comments

Excellent article providing the critical analysis side to a seemingly disturbing trend. Thank you for taking the time to put it together and disseminate to those of us who definitely are not ‘in the know’.

Quite possibly it’s from a ‘clever’ waterman who has developed a sonic orca call sign, that is solar-powered and operated from some secret place in False Bay.
Just wondering. Not too difficult to do. I’m surprised there is yet no development to replace the current ankle-worn shark-off with an underwater whistle attached to a surfers leash and that mimics the orca.
What’s orca for “I’m hungry for white shark liver”?